A dense mesh for tunnel overbreakage treatment

Abstract

The utility model discloses a dense mesh for tunnel overbreak disposal, include: polymer nanometer fiber matrix layer, cementing layer and nap layer, the polymer nanometer fiber matrix layer is net structure, the bottom surface of cementing layer is connected in the surface of polymer nanometer fiber matrix layer, the nap layer includes the intensive distribution's nanometer grade particle, and the nanometer grade particle is embedded in the cementing layer, and can protrude on the surface of cementing layer and form the protruding structure. Have corrosion resistance, can realize better net effect, prevent the drop.

Description

Technical Field

[0001] This utility model relates to the field of transportation and tunnel technology, and in particular to a dense mesh net for handling tunnel over-excavation. Background Technology

[0002] Over-excavation is a common problem in drill-and-blast tunnel construction. Over-excavation refers to the portion of the tunnel outside the designed excavation outline. The main causes of over-excavation include inadequate control of drill-and-blast holes and localized rock spalling. Drill-and-blast excavation involves hole construction, blasting and muck removal, excavation surveying, and quality inspection. The location, outward inclination angle, and depth of surrounding holes are all crucial during hole construction; inadequate control can lead to over-excavation. Disturbed joints and localized rock spalling can also cause over-excavation. After tunnel over-excavation, the use of dense mesh netting is of paramount importance. Firstly, if the over-excavated area is not addressed promptly, it can alter the stress distribution of the surrounding rock. The originally stable rock structure may loosen or collapse due to stress concentration, seriously threatening tunnel construction safety and subsequent operational stability. Secondly, if the voids created by over-excavation are not filled, they will reduce the integrity and load-bearing capacity of the tunnel structure, affecting its service life. Dense mesh netting provides effective support and guidance for subsequent filling operations, ensuring that the filling material is evenly and densely applied to the over-excavated area, thereby restoring the integrity and stability of the tunnel structure.

[0003] Dense mesh used for tunnel over-excavation treatment needs to possess a series of specific characteristics. First, it must have good flexibility. Tunnel walls often have irregular shapes and complex geological conditions; flexible mesh can tightly adhere to the wall surface, preventing gaps due to unevenness and ensuring effective filling. Second, it needs sufficient strength. Third, the surface roughness of the mesh is also crucial. A rough surface increases friction with the filling material, improving adhesion and preventing slippage or detachment, thus ensuring filling quality. Furthermore, the mesh should possess a certain degree of corrosion resistance to cope with potential corrosive factors such as chemicals and moisture present in the tunnel, extending its service life and reducing maintenance costs. Utility Model Content

[0004] To improve the contact cohesion with the filling material, this utility model provides a dense mesh net for tunnel over-excavation treatment, which is corrosion resistant, can achieve better netting effect, and prevents detachment.

[0005] This utility model embodiment provides a dense mesh net for tunnel over-excavation treatment, comprising: a polymer nanofiber matrix layer, an adhesive layer, and a fleece layer;

[0006] The polymer nanofiber matrix layer has a network structure;

[0007] The bottom surface of the adhesive layer is connected to the surface of the polymer nanofiber matrix layer;

[0008] The fluff layer comprises densely distributed nanoscale particles embedded in the adhesive layer and capable of protruding from the surface of the adhesive layer to form a protruding structure.

[0009] Optionally, the nanoscale particles may be made of silica particles or polymer microparticles, with a particle size range of 50 nm to 500 nm.

[0010] Optionally, the average height of the protrusion structure is 0.5μm to 50μm, and the density is greater than 1000 protrusions / mm².

[0011] Optionally, the ratio of the protrusion height to the particle size of the protrusion structure is 1:1 to 5:1.

[0012] Optionally, the adhesive layer may be made of a thermosetting resin layer with a thickness of 5 μm to 100 μm.

[0013] Optionally, the overall thickness of the polymer nanofiber matrix layer, the adhesive layer, and the fluff layer is 0.1 mm to 2.0 mm, and the peel strength is ≥1.0 N / cm.

[0014] Optionally, the polymer nanofiber matrix may be made of polyethylene.

[0015] The beneficial effects of the above-mentioned technical solutions provided in the embodiments of this utility model include at least the following:

[0016] This invention provides a dense mesh net for tunnel over-excavation treatment. The dense mesh net comprises a polymer nanofiber matrix layer, an adhesive layer, and a fleece layer arranged sequentially. The polymer nanofiber matrix layer has a mesh structure with a high specific surface area and good flexibility, adapting to the irregular shape of the over-excavated portion of the tunnel. Furthermore, using polymer nanofiber as the matrix material offers better corrosion resistance compared to traditional metal materials, effectively resisting the erosion of various corrosive factors in the tunnel environment, extending the service life of the dense mesh net, and reducing maintenance and replacement costs. By setting a fleece layer containing nanoscale particles outside the polymer nanofiber matrix layer, with the nanoscale particles embedded in the adhesive layer and protruding to form a raised structure, the surface roughness and micro-anchoring points of the entire dense mesh net are significantly increased, thereby greatly improving the contact cohesion with the filling material, making the bond between the two tighter. Compared to traditional hanging nets, the hanging effect is better, effectively preventing mesh detachment and enhancing the integrity and durability of tunnel over-excavation treatment. The polymer nanofiber matrix layer and the fluff layer are connected by an adhesive layer to form a three-dimensional mesh structure with stronger overall performance. This can improve the tensile strength, shear strength and other mechanical properties of the dense mesh, making it better able to resist various external forces and ensuring the safety of tunnel over-excavation treatment.

[0017] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0018] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 This is a schematic diagram of the structure of the dense mesh netting for tunnel over-excavation treatment provided in an embodiment of this utility model;

[0021] Figure 2 This is a schematic diagram of the initial support structure of the tunnel provided in the embodiment of this utility model;

[0022] Figure 3 This is an overall structural diagram of an example of tunnel over-excavation treatment provided in this embodiment of the present utility model;

[0023] Figure 4 This is a partial structural diagram of an example of tunnel over-excavation treatment provided in an embodiment of this utility model;

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. Polymer nanofiber matrix layer; 2. Adhesive layer; 3. Fleece layer; 4. Dense mesh; 5. Joint. Detailed Implementation

[0026] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0027] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "far," "near," "front," and "rear," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0029] The inventors discovered that existing dense mesh netting used for tunnel over-excavation treatment generally employs metal dense mesh netting and traditional hanging netting, but these commonly used dense mesh nettings have limitations and cannot fully meet the specific characteristics of dense mesh netting. Metal dense mesh netting is prone to rusting and rotting in the humid environment of tunnels, reducing the strength of the netting, affecting its long-term stability, and increasing maintenance costs and safety risks.

[0030] Traditional wire mesh and shotcrete rely primarily on the encapsulating force and friction of the concrete for bonding, resulting in low bond strength. During concrete pouring and setting, factors such as vibration and air bubbles can easily cause weak bonding, leading to quality problems such as mesh detachment and hollow areas, affecting the overall quality of tunnel over-excavation treatment. For irregular surface shapes in over-excavated tunnel areas, traditional wire mesh is difficult to adhere tightly, resulting in small local bonding areas and failing to fully exert the reinforcing effect of the mesh, posing safety hazards.

[0031] To address the aforementioned issues, the inventors developed a dense mesh netting for handling over-excavation in tunnels. This netting is corrosion-resistant, provides better hanging effect, and prevents detachment. Example

[0032] See Figure 1This embodiment proposes a dense mesh net for tunnel over-excavation treatment. The dense mesh net comprises a polymer nanofiber matrix layer 1, an adhesive layer 2, and a fluff layer 3 arranged sequentially. Specifically, the adhesive layer 2 is disposed between the polymer nanofiber matrix layer 1 and the fluff layer 3, primarily serving to connect the polymer nanofiber matrix layer 1 and the fluff layer 3. The polymer nanofiber matrix layer 1 has a mesh structure. The bottom surface of the adhesive layer 2 is connected to the surface of the polymer nanofiber matrix layer 1. The fluff layer 3 comprises densely distributed nano-sized particles embedded in the adhesive layer 2 and capable of protruding from the surface of the adhesive layer 2 to form a protruding structure.

[0033] In this embodiment, the polymer nanofiber matrix layer 1 has a mesh structure with a high specific surface area and good flexibility, which can adapt to the irregular shape of the over-excavated part of the tunnel. At the same time, using polymer nanofiber as the matrix material has better corrosion resistance than traditional metal materials, which can effectively resist the erosion of various corrosive factors in the tunnel environment, extend the service life of the dense mesh, and reduce maintenance and replacement costs.

[0034] In this embodiment, by setting a fluff layer 3 containing nanoscale particles outside the polymer nanofiber matrix layer 1, the nanoscale particles are embedded in the adhesive layer 2 and protrude to form a protruding structure, which can significantly increase the roughness and micro-anchoring points of the entire dense mesh surface, thereby greatly improving the contact cohesion with the filling material (such as concrete), making the two more tightly bonded. Compared with traditional mesh, the mesh hanging effect is better, effectively preventing the mesh from falling off, and enhancing the integrity and durability of tunnel over-excavation treatment.

[0035] In this embodiment, the polymer nanofiber matrix layer 1 and the fluff layer 3 are connected by the adhesive layer 2 to form a three-dimensional mesh structure with stronger overall performance. This can improve the tensile strength, shear strength and other mechanical properties of the dense mesh, enabling it to better resist various external forces and ensure the safety of tunnel over-excavation treatment.

[0036] In one specific embodiment, the nanoparticles are made of silica particles. Silica particles are characterized by high hardness and good chemical stability. When the silica particles protrude from the surface of the adhesive layer as nanoparticles, the abundant silanol groups and other active groups on the surface of the silica particles can chemically react with the cement hydration products in the filler material (such as concrete) to form chemical bonds, thereby significantly enhancing the adhesion between the mesh and the filler material. This chemical bonding is stronger than simple physical bonding, effectively reducing the interfacial voids between the filler material and the mesh, and improving the overall quality of tunnel over-excavation treatment. Simultaneously, during tunnel construction and use, the mesh may be subjected to a certain degree of friction and wear. The high hardness of the silica particles enables them to withstand these external forces, reducing wear on the pile layer and extending the service life of the mesh. Even during long-term use, the pile layer can still maintain a good protruding structure, continuously playing a role in enhancing adhesion.

[0037] In one specific embodiment, the nanoparticles are made of polymer microparticles. These polymer microparticles possess a certain degree of flexibility and elasticity, allowing them to deform to some extent without breaking under external force. This characteristic makes the mesh more flexible in adapting to the irregular shape of the tunnel wall and deformation during construction, enabling it to better conform to the wall and reduce damage caused by stress concentration. Simultaneously, the flexibility of the polymer microparticles also helps maintain the stability of the raised structure of the pile layer, making it less prone to damage during long-term use. Since both the polymer microparticles and the polymer nanofiber matrix layer are made of polymers, they have good compatibility, allowing them to bond tightly together to form a unified whole. This good compatibility helps improve the structural stability of the mesh, reduces stress concentration at the interface, and allows the mesh to distribute stress more evenly under load, thereby improving its load-bearing capacity and resistance to damage.

[0038] In one specific embodiment, the particle size of the nanoparticles ranges from 50 nm to 500 nm. At this scale, nanoparticles have a large specific surface area. A larger specific surface area means an increased contact area between the nanoparticles and the filler material, thereby providing more bonding sites and enhancing the bonding effect. If the particle size of the nanoparticles is small (less than 50 nm), they are prone to agglomeration, leading to uneven distribution of nanoparticles in the fluff layer, affecting the formation and performance of the protrusion structure, and thus reducing the bonding effect between the mesh and the filler material. If the particle size of the nanoparticles is large (greater than 500 nm), the height of the formed protrusion structure may be too high, hindering the flow of the filler material, slowing down the flow rate, and even causing local accumulation and voids, affecting the density and uniformity of the filler, and reducing the bonding effect between the mesh and the filler material.

[0039] Referring to Table 1, the performance of each mesh was measured using silica particles of different sizes as the flock layer. It can be found that the 500nm silica particles have the best bonding strength and excellent adhesion, indicating that the nanoscale particles with a particle size range of 50nm-500nm have the best performance.

[0040] Table 1. Performance comparison of silica particles with different particle sizes

[0041]

[0042] In one specific embodiment, the average height of the protruding structures is 0.5μm to 50μm, and the density is greater than 1000 protrusions / mm². If the average height of the protruding structures is low (e.g., below 0.5μm), the protruding structures cannot provide sufficient anchoring force in the filling material, resulting in weak adhesion between the mesh and the filling material. This can easily lead to problems such as filling material detachment and slippage, affecting the quality and stability of tunnel over-excavation treatment. Furthermore, when the average height of the protruding structures is below 0.5μm, the effect of the protruding structures on increasing the contact area is very limited. This is because the increase in contact area is related to the height and density of the protruding structures. With a fixed density, a small height means that the space occupied by the protruding structures in the filling material is limited, and the contact area between the two cannot be significantly increased, resulting in poor adhesion. If the average height of the protruding structures is high (e.g., above 50μm), the protruding structures will hinder the flow of the filling material. During the flow process, the filling material will be blocked by the protruding structures, resulting in a slower flow velocity and even local accumulation and voids. A protrusion density greater than 1000 per mm² means that there are a large number of protrusions per unit area. These densely distributed protrusions can significantly increase the contact area between the mesh and the filler material, further enhancing the bonding effect between the two. Moreover, the high-density protrusions can make the filler material more evenly distributed on the surface of the mesh, reducing local accumulation and voids of the filler material and improving the compactness of the filler.

[0043] Referring to Table 2, in this embodiment, the protrusion height of mesh 1 did not meet the standard, but the protrusion density did; in this embodiment, the protrusion height of mesh 2 met the standard, but the protrusion density did not; in this embodiment, both the protrusion height and density of mesh 3 met the standards. By comparing mesh 1, mesh 2, and mesh 3 in this embodiment, it can be found that the lowest detachment rate (concrete detachment rate) occurs only when the average height of the protrusion structure is 0.5μm~50μm and the density is greater than 1000 protrusions / mm². By comparing traditional embossed PVC panels and mesh 3 in this embodiment, it can be found that the mesh in this embodiment has a lower detachment rate and a better hanging effect.

[0044] Table 2 Comparative experimental results of dense mesh and traditional embossed PVC board in this embodiment

[0045]

[0046] In one specific embodiment, the adhesive layer is made of a thermosetting resin layer. The thermosetting resin forms a three-dimensional mesh structure during curing, exhibiting high mechanical strength. In tunnel over-excavation treatment, the mesh needs to withstand the weight of the filling material and potential external forces. The thermosetting resin layer provides reliable bonding strength, ensuring a tight bond between the mesh and the filling material, preventing detachment or damage.

[0047] In one specific embodiment, the thickness of the adhesive layer is 5 μm to 100 μm. The thickness of the adhesive layer directly affects its contact area and adhesion strength with the polymer nanofiber matrix layer and the fluff layer. When the adhesive layer thickness is less than 5 μm, it cannot provide sufficient bonding area and adhesion strength to firmly connect the polymer nanofiber matrix layer and the fluff layer. When the adhesive layer thickness is greater than 100 μm, the increased thickness means that more adhesive material needs to be used, thereby increasing material costs.

[0048] In one specific embodiment, the ratio of the protrusion height to the particle size of the protrusion structure is 1:1 to 5:1. When the ratio of the protrusion height to the particle size is less than 1:1, the protrusion structure is relatively flat and cannot penetrate deep into the filling material to form effective embedding, thus reducing the bonding strength. When the ratio of the protrusion height to the particle size is greater than 5:1, stress concentration causes the roots of the nanoparticles to break, reducing the bonding strength.

[0049] Referring to Table 3, which compares the bonding strength of protrusion structures with different protrusion height to particle size ratios, it can be found that the bonding strength is the greatest when the ratio of protrusion height to particle size is 5:1. Therefore, the ratio of protrusion height to particle size should be 1:1 to 5:1.

[0050] Table 3. Comparison of bonding strength of protrusion structures with different protrusion height-to-particle size ratios.

[0051]

[0052] In one specific embodiment, the overall thickness of the polymer nanofiber matrix layer, adhesive layer, and pile layer is 0.1mm to 2.0mm. An overall thickness greater than 2mm leads to a decrease in the overall flexibility of the material, making it difficult to adapt to complex curved surfaces or applications requiring bending, and preventing it from adhering to rock surfaces. An overall thickness less than 0.1mm results in reduced mechanical properties, making it difficult to withstand significant external forces or wear. Peel strength is an important indicator of the bonding strength between the polymer nanofiber matrix layer, adhesive layer, and pile layer. A peel strength ≥1.0N / cm ensures that these three layers will not easily delaminate or detach during use, guaranteeing the overall performance and service life of the mesh.

[0053] In one specific embodiment, the polymer nanofiber matrix is ​​made of polyethylene. Polyethylene has good chemical stability, and tunnel seepage environments often contain corrosive substances such as sulfates. The C-C bond structure of polyethylene is more resistant to chemical erosion than other polymers (such as polyesters, polyamides, etc.).

[0054] For example, the production process of the dense mesh in this embodiment can adopt the melt-blown method, which may specifically include the following steps:

[0055] Step S101: Polymer chips are fed into a screw extruder, melted, and then extruded through a spinneret.

[0056] Step S102: High-speed, high-temperature airflow blows the melt, stretching the melt into nanofibers to obtain a polymer nanofiber matrix;

[0057] In step S102 above, based on existing processes, the temperature of the high-temperature gas flow is 300°C-400°C.

[0058] Step S103: Before the polymer nanofiber matrix cools down, electrostatic spraying or co-forming technology is integrated to uniformly attach nanoscale particles to the surface of the polymer nanofiber matrix to form a protruding structure and obtain a fluff layer.

[0059] In step S103 above, the nanoscale can also adopt a bicomponent fiber design, wherein the soluble component is dissolved in the post-processing, leaving the protruding structure.

[0060] Step S104: Form a fiber web by combining the polymer nanofiber matrix and the pile layer, and connect the polymer nanofiber matrix and the pile layer by thermal bonding, that is, form an adhesive layer between the polymer nanofiber matrix and the pile layer to obtain a dense mesh.

[0061] In step S104 above, after forming the dense mesh, further processing can be carried out before winding to optimize compatibility with concrete, and finally the edges are trimmed and the mesh is wound up.

[0062] In the above production process, the airflow speed, temperature and spraying parameters are controlled throughout to ensure the uniformity of the pile layer and improve the functionality of the product.

[0063] See Figure 3 and Figure 4 This embodiment illustrates the application of concrete formwork in tunnel over-excavation treatment. Figure 3 The green area represents the over-excavation and backfilling area, and the area indicated by the red border is the coverage area of ​​the isolation net. When implementing tunnel over-excavation construction, based on the existing initial support technology, the dense mesh netting shown in Example 1 is used instead of the metal dense mesh netting or traditional hanging netting. (See also...) Figure 2Connect the dense mesh 4 and the reinforcing mesh using joint 5; during the initial support construction, the dense mesh 4 and the reinforcing mesh are perforated from the rock wall. Apply shotcrete to the initial support. (See [reference needed]). Figure 4 When spraying the initial support concrete, a backfill hole needs to be reserved. The diameter of the backfill hole is 450mm, and a PVC pipe (with a hole in the side wall) is inserted into the rock wall. When spraying the initial support concrete, a rubber plug is used to seal the pipe opening to avoid blockage of the inlet. The spacing between the backfill holes is 1.0m in the circumferential direction and 0.5m in the longitudinal direction.

[0064] Once the initial support concrete reaches 70% strength, grouting is performed through the backfill holes at a pressure of 0.2–0.5 MPa. Grouting proceeds from the lowest point to the highest. Grouting is stopped when grout flows out of the vent holes; the grouting holes are then sealed, and pressure grouting continues through the vent holes. The grouting is stopped after 10 minutes of grout absorption. Within 30 minutes of grouting completion, the holes are sealed with cement grout of equivalent initial support strength: the sealing material is slowly injected into the grouting holes until grout overflows from the opening; the opening is then plugged with a wooden stopper. After the sealing material solidifies, an inspection is conducted to ensure the sealing quality, completing the over-excavation treatment. This process is simple, effective, and demonstrates significant cost reduction and efficiency improvement.

[0065] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. This disclosure is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims. Thus, if these modifications and variations of this utility model fall within the scope of the claims of this utility model and their equivalents, then this utility model is also intended to include these modifications and variations.

Claims

1. A wire mesh for tunnel overbreakage treatment, characterized in that, include: Polymer nanofiber matrix layer, adhesive layer and fluff layer; The polymer nanofiber matrix layer has a network structure; The bottom surface of the adhesive layer is connected to the surface of the polymer nanofiber matrix layer; The fluff layer comprises densely distributed nanoscale particles embedded in the adhesive layer and capable of protruding from the surface of the adhesive layer to form a protruding structure.

2. The wire mesh for tunnel overbreakage treatment according to claim 1, characterized in that, The nanoscale particles are made of silica particles or polymer microparticles, with a particle size range of 50nm to 500nm.

3. The close-meshed net for tunnel overbreakage treatment according to claim 1, characterized in that, The average height of the protrusions is 0.5μm to 50μm, and the density is greater than 1000 per mm².

4. The wire mesh for tunnel overbreakage treatment according to claim 3, characterized in that, The ratio of the protrusion height to the particle size of the protrusion structure is 1:1 to 5:

1.

5. The dense mesh netting for tunnel over-excavation treatment according to claim 1, characterized in that, The adhesive layer is made of thermosetting resin and has a thickness of 5μm to 100μm.

6. The dense mesh netting for tunnel over-excavation treatment according to claim 1, characterized in that, The overall thickness of the polymer nanofiber matrix layer, the adhesive layer, and the fluff layer is 0.1 mm to 2.0 mm, and the peel strength is ≥1.0 N / cm.

7. The dense mesh netting for tunnel over-excavation treatment according to any one of claims 1-6, characterized in that, The polymer nanofiber matrix is ​​made of polyethylene.

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